1. Field of Invention
The invention relates to methods and apparatus for adaptably controlling the series hybrid electric vehicle.
2. Description of Related Art
The desire for cleaner air has caused various federal, state, and local governments to change their regulations to require lower vehicle emissions. Increasing urban traffic congestion has prompted a need for increases in public mass transit services. Many large cities use buses to transport people into, out of, and within traffic congested urban areas. Conventional buses use diesel powered internal combustion engines. Diesel engines produce emissions, including carbon monoxide, that contribute to air pollution. It is possible to refine cleaner diesel fuel. However, cleaner diesel fuel is more costly to refine and causes a corresponding increase in the cost of bus service.
Alternative fuels have been used to reduce emissions and conserve oil resources. Compressed natural gas has been used as an alternative fuel. Compressed natural gas does not produce as much power in conventional internal combustion engines as gasoline and diesel and has not been widely developed or accepted as an alternative to gasoline and diesel.
Additives have also been developed for mixing with gasoline to reduce emissions. Ethanol and MTBE have been added to gasoline to oxygenate the combustion of gasoline and reduce emissions of carbon monoxide. These additives, however, are believed to cause decreased gas mileage and, in the case of MTBE, to be a potential public health threat.
Electric vehicles have been developed that produce zero emissions. Electric vehicles are propelled by an electric motor that is powered by a battery array on board the vehicle. The range of electric vehicles is limited as the size of the battery array which can be installed on the vehicle is limited. Recharging of the batteries can only be done by connecting the battery array to a power source. Electric vehicles are not truly zero emitters when the electricity to charge the battery array is produced by a power plant that bums, for example, coal.
Hybrid electric vehicles have also been developed to reduce emissions. Hybrid electric vehicles include an internal combustion engine and at least one electric motor powered by a battery array. In a parallel type hybrid electric vehicle, both the internal combustion engine and the electric motor are coupled to the drive train via mechanical means. The electric motor may be used to propel the vehicle at low speeds and to assist the internal combustion engine at higher speeds. The electric motor may also be driven, in part, by the internal combustion engine and be operated as a generator to recharge the battery array.
In a series type hybrid electric vehicle, the internal combustion engine is used only to run a generator that charges the battery array. There is no mechanical connection of the internal combustion engine to the vehicle drive train. The electric traction drive motor is powered by the battery array and is mechanically connected to the vehicle drive train.
In present series type hybrid electric vehicles, there is a need to control the engine, generator and electric motor according to the emission environment. In one emission environment, the engine is running at a selected operating speed. However, in a second emission environment, the engine is turned off. There is thus a need to control this engine, generator and electric motor to reduce engine wear during engine start up as the engine operates in the various operating modes. There is also a need to control the engine, generator and electric motor to reduce engine wear of the engine and to remove excess fuel during engine shut off.
The invention provides methods and apparatus for adaptively managing the internal combustion engine, generator, and electric motor for a series type hybrid electric vehicle.
An exemplary embodiment of a series type hybrid electric vehicle according to the invention is controlled so that a generator set of the vehicle, including an internal combustion engine connected to a generator, reduces the load applied to the internal combustion engine when the internal combustion engine is restarted, lowers the thermal stresses to the internal combustion engine when the engine is turned off and is able to remove excess fuel when turning off the internal combustion engine.
According to an exemplary embodiment, a method for adaptively controlling the state of charge of a battery array of a series type hybrid electric vehicle having an internal combustion engine connected to a generator and at least one electric motor with the internal combustion engine and generator selectively operated in various operation modes consisting of operating the vehicle in a first mode in which the internal combustion engine and generator are off and the motor propels the vehicle from power stored in the battery array, operating the vehicle in a second mode in which the internal combustion engine and generator are operating without restriction, and operating the vehicle in a third mode in which the operation of the internal combustion engine and generator are at least partially restricted to limit vehicle discharges.
According to another exemplary embodiment, a series type hybrid electric vehicle includes an internal combustion engine connected to a generator, a battery array receiving current at least from the generator, at least one electric motor receiving current from the battery array, and a controller that selectively operates the engine and generator in various operating modes, including a first mode in which the internal combustion engine and generator are off and the motor propels the vehicle from power stored in the battery array, a second mode in which the internal combustion engine and generator are operating without restriction, and a third mode in which the operation of the internal combustion engine and generator are at least partially restricted to limit vehicle discharges.
Other features of the invention will become apparent as the following description proceeds and upon reference to the drawings.